I have seen this question worded in the following way:
A dog with a 20 ft leash is tied to the corner of a building which is 22 ft by 15ft.
What is the area that the dog can cover?
make a sketch.
clearly he can reach 20 ft down along the building.
If he goes the other way, he can move around the corner, cover the 15 ft along the width of the building and wrap around another 5 ft down the length of the opposite side of the long building
So I see 3/4 of a circle with radius 20, and 1/4 of a circle with radius 5